U.S. patent application number 12/513626 was filed with the patent office on 2009-10-01 for display element.
This patent application is currently assigned to KONICA MINOLTA HOLDINGS, INC.. Invention is credited to Noriyuki Kokeguchi.
Application Number | 20090243462 12/513626 |
Document ID | / |
Family ID | 39364334 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090243462 |
Kind Code |
A1 |
Kokeguchi; Noriyuki |
October 1, 2009 |
DISPLAY ELEMENT
Abstract
This invention provides a display element having a reduced white
color tone variation during repeated drive. This display element
contains an electrolyte between opposed electrodes. The electrolyte
contains silver or a compound containing silver in its chemical
structure. The opposed electrodes are driven so that silver is
dissolved and precipitated. The display element is characterized in
that the electrolyte contains a compound represented by general
formula (A) and a compound represented by general formula (1) or
(2).
Inventors: |
Kokeguchi; Noriyuki; (Tokyo,
JP) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
KONICA MINOLTA HOLDINGS,
INC.
Tokyo
JP
|
Family ID: |
39364334 |
Appl. No.: |
12/513626 |
Filed: |
October 15, 2007 |
PCT Filed: |
October 15, 2007 |
PCT NO: |
PCT/JP2007/070061 |
371 Date: |
May 5, 2009 |
Current U.S.
Class: |
313/483 |
Current CPC
Class: |
G02F 1/1506
20130101 |
Class at
Publication: |
313/483 |
International
Class: |
H01J 1/62 20060101
H01J001/62 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2006 |
JP |
2006-302596 |
Claims
1. A display element comprising an electrolyte containing silver or
a compound containing silver in the chemical structure thereof
between opposed electrodes, and carrying out driving operation for
the opposed electrodes to induce silver dissolution and deposition,
wherein the electrolyte contains a compound represented by Formula
(A); and a compound represented by Formula (1) or Formula (2):
##STR00014## wherein X and Y each represent an alkyl group having 1
to 4 carbon atoms, provided that they may be the same or different;
"k" and "i" each represent an integer of 0 to 4; "m" and "n" each
represent an integer of 3 to 7; and "A" represents an acid
component, R.sub.7--S--R.sub.8 Formula (1) wherein R.sub.7 and
R.sub.8 each represent a substituted or unsubstituted hydrocarbon
group, provided that an aromatic ring is not included when a ring
containing a sulfur atom is formed: ##STR00015## wherein, M is a
hydrogen atom, a metal atom or a quaternary ammonium; Z represents
a nitrogen containing heterocylic group; "n" represents an integer
of 0 to 5; R.sub.9 represents a hydrogen atom, a halogen atom, an
alkyl group, an aryl group, an alkylcarbonamide group, an
arylcarbonamide group, an alkylsulfonamide group, an
arylsulfonamide group, an alkoxy group, an aryloxy group, an
alkylthio group, a arylthio group, an alkylcarbamoyl group, an
arylcarbamoyl group, a carbamoyl group, an alkylsulfamoyl group, an
arylsulfamoyl group, a sulfamoylmoyl group, a cyano group, an
alkylsulfonyl group, an arylsulfonyl group, an alkoxycarbonyl
group, an aryloxycarbonyl group, an alkylcarbonyl group, an
arylcarbonyl group, an acyloxy group, a carboxyl group, a carbonyl
group, a sulfonyl group, an amino group, a hydroxyl group or a
heterocyclic group, provided that when "n" is two or more, plural
R.sub.9s may be the same or different, the plural R.sub.9s may be
joined to form a ring which forms a condensed ring.
2. The display element of claim 1, wherein a sum of "m" and "n" in
Formula (A) is 8.
3. The display element of claim 1, wherein the compound represented
by Formula (A) is a triazole derivative.
4. The display element of claim 1, wherein a condition specified by
the following expression (1) is satisfied, provided that [X] is a
molar concentration of a halogen ion and a halogen atom contained
in the electrolyte and is expressed in mol/kg; and [Ag] is a total
molar concentration of silver and a compound containing the silver
in its chemical structure, contained in the electrode and is
expressed in mol/kg: 0.ltoreq.[X]/[Ag].ltoreq.0.1. Expression (1)
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrochromic display
element employing silver dissolution and deposition.
BACKGROUND
[0002] In recent years, with enhancement of operation speed of
personal computers, widespread use of network infrastructure, and
realization of mass storage of data, as well as cost reduction of
data storage, there are increasing occasions in which information
of documents and images, having been conventionally provided in the
form of printed paper matter, is received and viewed as more
convenient electronic information.
[0003] As viewing methods for such electronic information, there
are mainly used those which are of light emitting types such as
conventional liquid crystal display devices and CRTs, or organic EL
display devices, which have recently been marketed. Especially,
however, when electronic information is composed of items of
document information, it is necessary to stare at these viewing
devices for a relatively long time, which is certainly not
viewer-friendly. It is commonly known that light emitting type
display devices have disadvantages such as eye fatigue due to
flicker, inconvenience of portability, limited reading posture,
necessity to look closely at still images, and high power
consumption due to the use of these devices for long-time
reading.
[0004] As display devices to overcome these disadvantages, there
are known memory effect reflective display devices, which utilize
external light, resulting in consuming no electrical power to
retain images. However, these devices do not exhibit adequate
performance due to the following reasons.
[0005] Namely, a system, employing a polarizing plate such as a
reflective type liquid crystal, creates a problem in white display
due to its low reflectance of approximately 40%, and most of the
production methods of constituent members are neither simple nor
easy. Further, polymer dispersion type liquid crystals require a
high operating voltage and exhibit poor contrast of resultant
images due to the utilization of a refractive index difference
between the used organic compounds. Still further, polymer network
type liquid crystals have problems such that high operating
voltages result and complicated TFT circuits are required to
enhance memory capability. Yet further, display elements employing
electrophoresis require a high operating voltage of at least 10 V
and tend to exhibit low operation life due to electrophoretic
particle aggregation. In contrast, although being drivable at a low
voltage of at most 3 V, electrochromic display elements have the
disadvantage of exhibiting poor color quality of black or colors
(such as yellow, magenta, cyan, blue, green, and red), as well as
having the disadvantage that each display cell requires a
complicated film structure such as a vapor deposition film to
ensure memory capability.
[0006] As a display system to overcome any of the disadvantages in
each of the systems described above, there is known an electrode
deposition (hereinafter referred to simply as ED) system employing
dissolution and deposition of a metal or metallic salt. The ED
system is drivable at a low voltage of at most 3 V, and features
advantages such as a simple cell structure and excellence in black
and white contract, as well as in black image quality, resulting in
disclosure of a variety of systems (for example, refer to Patent
Documents 1-3).
[0007] The present inventor has made detailed investigation in the
technologies disclosed in each of the Patent Documents described
above, and found that these conventional technologies have problems
of exhibiting color change of white color during white display
after accumulated repeating driving operation. In addition, it is
known that an onium cation is applied for an electrolytic capacitor
(for example, refer to Patent Documents 4-5). However, its
application to a display element was not described or suggested.
[0008] Patent Document 1: U.S. Pat. No. 4,240,716 specification
[0009] Patent Document 2: Japanese Patent Publication No. 3428603
[0010] Patent Document 3: Unexamined Japanese Patent Application
Publication No. 2003-241227 [0011] Patent Document 4: Japanese
Patent Publication No. 2701874 [0012] Patent Document 5: Unexamined
Japanese Patent Application Publication No. 2005-5357
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0013] In view of the above problems, the present invention was
achieved. An object of the present invention is to provide a
display element exhibiting a decreased color change in white
display after repeated driving operation of the display
element.
Means to Solve the Problems
[0014] The object of the present invention was achieved employing
the following constitutions.
1. A display element comprising an electrolyte containing silver or
a compound containing silver in the chemical structure thereof
between opposed electrodes, and carrying out driving operation for
the opposed electrodes to induce silver dissolution and deposition,
wherein the electrolyte contains a compound represented by the
following Formula (A); and a compound represented by the following
Formula (1) or Formula (2).
##STR00001##
[0015] (In Formula, X and Y each represent an alkyl group having to
4 carbon atoms, and they may be the same or different. "k" and "i"
each represent 0 or a positive integer of 1 to 4; and "m" and "n"
each represent a positive integer of 3 to 7. "A" represents an acid
component.)
R.sub.7--S--R.sub.8 Formula (1)
[0016] (In Formula, R.sub.7 and R.sub.8 each represent a
substituted or unsubstituted hydrocarbon group, provided that an
aromatic ring is not included when a ring containing a sulfur atom
is formed.)
##STR00002##
[0017] (In Formula, M is a hydrogen atom, a metal atom or a
quaternary ammonium. Z represents a nitrogen containing heterocylic
group. "n" represents an integer of 0 to 5. R.sub.9 represents: a
hydrogen atom, a halogen atom, an alkyl group, an aryl group, an
alkylcarbonamide group, an arylcarbonamide group, an
alkylsulfonamide group, an arylsulfonamide group, an alkoxy group,
an aryloxy group, an alkylthio group, a arylthio group, an
alkylcarbamoyl group, an arylcarbamoyl group, a carbamoyl group, an
alkylsulfamoyl group, an arylsulfamoyl group, a sulfamoyl group, a
cyano group, an alkylsulfonyl group, an arylsulfonyl group, an
alkoxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl
group, an arylcarbonyl group, an acyloxy group, a carboxyl group, a
carbonyl group, a sulfonyl group, an amino group, a hydroxyl group,
or a heterocyclic group. When "n" is two or more, plural R s may be
the same or different, and further, they may be joined to form a
ring resulting in forming a condensed ring.)
2. The display element described in the aforesaid item 1, wherein a
total of "m" and "n" in Formula (A) is 8. 3. The display element
described in the aforesaid item 1 or item 2, wherein the compound
represented by Formula (A) is a triazole derivative. 4. The display
element described in one of the aforesaid items 1 to 3, wherein the
condition specified by the following expression (1) is satisfied,
provided that [X] is a total molar concentration of a halogen ion
and a halogen atom contained in the electrolyte and is expressed in
mol/kg; and [Ag] is a total molar concentration of silver and a
compound containing the silver in its chemical structure, contained
in the electrode and is expressed in mol/kg.
0.ltoreq.[X]/[Ag].ltoreq.0.01. Expression (1)
EFFECTS OF THE INVENTION
[0018] According to the present invention, it was achieved to
provide a display element which exhibits a decreased color change
in white display after repeated driving operation of the display
element.
BEST MODE TO CARRY OUT THE INVENTION
[0019] The best mode to carry out the present invention will now be
detailed.
[0020] In view of the above problems, the present inventor
conducted diligent investigations and realized the following: a
display element having opposed electrodes and an electrolyte layer
incorporating silver or a compound containing silver in its
chemical structure between the opposed electrodes; and by carrying
out driving operation for the opposed electrodes to induce silver
dissolution and deposition, wherein the aforesaid electrolyte
contains a compound represented by Formula (A); and a compound
represented by Formula (1) or Formula (2). It was found that the
display element can realize a decreased color change in white
display even after repeated driving operation of the display
element.
[0021] In the constitution of the display element according to the
present invention, the compound represented by Formula (A) has an
effect of increasing an ion conductivity of the electrolyte,
thereby improving the speed of whitening or blackening of the
display element. Known compounds capable to increase such speed
are, for example: an imidazolium derivative, a pyridinium
derivative, an ammonium derivative and a pyrrolidinuim derivative.
It was found that these compounds may interact with silver ions in
the electrolyte, the composition of which is peculiar to the ED
method of the present invention, and the stability of the compound
itself may be insufficient resulting in insufficient reliability of
the display after repeated driving of the display element. It was
revealed that the compound represented by Formula (A) of the
present invention will not interact with silver ions and it can
achieve both properties at the same time: speed of blackening and
whitening; and display reliability of the display element.
[0022] The present invention will now be detailed.
[0023] The display element of the present invention is an ED system
display element having an electrolyte, incorporating silver or a
compound containing silver in its chemical structure, between
opposed electrodes, and carrying out driving operation for the
opposed electrodes to induce silver dissolution and deposition.
(Electrolyte)
[0024] The display element of the present invention has an
electrolyte between a pair of electrodes. "Electrolyte" of the
present invention generally refers to a compound which dissolves in
a solvent such as water and the solution exhibits an ionic
conductivity (hereafter it is called as "an electrolyte in a narrow
definition"). However, in the description of the present invention,
a mixture of an electrolyte in a narrow definition and other metal
or compound (regardless of electrolytic or non-electrolytic) may be
also called as an electrolyte (such a mixture is called as "an
electrolyte in a broad definition".)
(Silver, or Compound Containing Silver in Chemical Structure)
[0025] A compound containing silver, or a compound containing
silver in their chemical structure, according to the present
invention, is common designations of a compound such as silver
oxide, silver sulfide, metallic silver, colloidal silver particles,
sliver halide, silver complex compound, or a silver ion. The phase
states such as a solid state, a state solubilized to liquid, a gas
state, and charge state types such as neutral, anionic or cationic
are not particularly considered.
(Basic Structure of the Display Element)
[0026] In the display element of the present invention, each ED
display portion has corresponding paired counter electrodes. An
electrode 1 of the paired counter electrodes positioned nearer to
the ED is provided with a transparent electrode such as ITO
electrode, while the other electrode 2 is provide with a metal
electrode such as silver electrode.
[0027] An electrolyte is sandwiched between electrode 1 and
electrode 2, and the electrolyte contains silver or a compound
having silver in the molecule. By applying voltage having a
positive and a negative polarity to the counter electrodes, an
oxidation-reduction reaction takes place on electrode 1 and
electrode 2. Thereby a black silver image of reduced state and a
transparent silver of oxidized state will be reversibly
interchanged.
[Compound Represented by Formula (A)]
[0028] The compound represented by Formula (A) of the present
invention will be described.
[0029] In Formula (A), when X and Y each represent an alkyl group
having 1-4 carbon atoms, and they may be the same or different. k
and i each represent 0 or a positive integer of 1 to 4; and m and n
each represent a positive integer of 3 to 7.
[0030] In Formula (A), when X and Y are equal to 5 or larger, and k
and i are equal to 5 or larger, or n and m are equal to 8 or
larger, ionic conductivity of the spiroammonium salt is decreased
to give an unwanted effect.
[0031] Examples of cations of spiroammonium salts in Formula (A)
are as follows: spiro-(1,1')-biazacyclobutyl ion,
azacyclopentane-1-spiro-1'-azacyclobutyl ion,
azacyclohexane-1-spiro-1'-azacyclobutyl ion,
azacycloheptane-1-spiro-1'-azacyclobutyl ion,
azacyclooctane-1-spiro-1'-azacyclobutyl ion,
spiro-(1,1')-biazacyclopentyl ion,
azacyclohexane-1-spiro-1'-azacyclopentyl ion,
azacycloheptane-1-spiro-1'-azacyclopentyl ion,
azacyclooctatane-1-spiro-1'-azacyclopentyl ion,
spiro-(1,1')-biazacyclohexyl ion,
azacycloheptane-1-spiro-1'-azacyclohexyl ion,
azacyclooctane-1-spiro-1'-azacyclohexyl ion,
spiro-(1,1')-biazacycloheptyl ion,
azacyclooctane-1-spiro-1'-azacycloheptyl ion,
spiro-(1,1')-biazacyclooctyl ion.
[0032] In Formula (A), A represents an acid component. Examples of
A are: a perchloric acid ion (ClO.sub.4.sup.-), a fluorine ion
(F.sup.-), a chlorine ion (Cl.sup.-), a bromine ion (Br.sup.-), an
iodine ion (I.sup.-), a hexafluorophosphoric acid ion
(PF.sub.6.sup.-), a hexafluoroantimonic acid ion (SbF.sub.6.sup.-),
a tetrafluoroboric acid ion (BF.sub.4.sup.-), a
trifluoromethanesulfonic acid ion (CF.sub.3SO.sub.3.sup.-), a
trifluoroacetic acid ion (CF.sub.3CO.sub.2.sup.-), a
bistrifluoromethanesulfonylimide ion
((CF.sub.3SO.sub.2).sub.2N.sup.-), a perfluorobutanesulfonic acid
ion (C.sub.4F.sub.9SO.sub.3.sup.-), a
tristrifluoromethanesulfonylmethyde ion
((CF.sub.3SO.sub.2).sub.3C.sup.-), a dicyanamide ion
((CN).sub.2N.sup.-), p-toluenesulfonic acid, a borate compound such
as bis[oxalate(2-)]borate. Among them, the ions containing no
halogen atoms, such as a dicyanamide ion ((CN).sub.2N.sup.-),
p-toluenesulfonic acid and bis[oxalate(2-)]borate are
preferable.
[0033] Spiroammonium salts represented by Formula (A) of the
present invention can be produced by the following method.
[0034] At first, an azacycloalkane is allowed to react with a
dibromoalkane which is substituted with two bromine atoms at two
terminal positions in isopropylalcohol under the presence of sodium
carbonate to obtain a spiroammonium bromide. Then, the obtained
bromide is subjected to electrodialytic desalination in water or
alcohol to obtain a spiroammonium hydroxide. The obtained
spiroammonium hydroxide solution is neutralized by adding an equal
amount of an acid component corresponding to "A" in Formula (1).
Then water is eliminated under reduced pressure and the targeted
spiroammonium salt can be obtained. Also, these compounds are
available as commercial products, for example, SBP--BF4 (produced
by Japan Carlit Co., Ltd.) can be cited.
[0035] An added amount of a compound represented by Formula (A) to
the electrolyte solution is preferably from 0.1 weight % to 10
weight %. When it is 0.1 weight % or more, the improved effect of
the present invention can be achieved. When it is 10 weight % or
less, it can be prevented from precipitating out in the electrolyte
solution at low temperature and it can be stably incorporated in
the electrolyte solution.
(Porous White Scattering Layer)
[0036] The display element of the present invention may incorporate
a porous white scattering layer from the viewpoint of enhancing
display contrast and white display reflectance.
[0037] The porous white scattering layers which can be applied to
the present invention are formed by coating and drying an aqueous
mixture of aqueous polymers substantially insoluble in the
electrolyte solvents and white pigment.
[0038] Examples of white pigments which can be used in the present
invention include: titanium dioxide (anatase or rutile type),
barium sulfate, calcium carbonate, aluminum oxide, zinc oxide,
magnesium oxide, zinc hydroxide, magnesium hydroxide, magnesium
phosphate, magnesium hydrogen phosphate, alkaline earth metallic
salts, talc, kaolin, zeolite, acid clay, glass, and organic
compounds such as polyethylene, polystyrene, acryl resins,
ionomers, ethylene-vinyl acetate copolymeric resins, benzoguanamine
resins, urea-formaldehyde resins, melamine-formaldehyde resins, or
polyamide resins. These substances may be uses individually or in
combination, or in the form in which voids, capable of varying the
refractive index, are contained in the particles.
[0039] In the present invention, titanium dioxide, zinc oxide and
zinc hydroxide are preferably employed among the-above described
white particles. Further, titanium oxide may be titanium oxide
which has been subjected to a surface treatment employing an
inorganic oxide (such as Al.sub.2O.sub.3, AlO(OH), or SiO.sub.2),
or titanium oxide which has been subjected to a treatment employing
an organic compound such as trimethylolethane, triethanolamine
acetic acid salts, or trimethylcyclosilane, in addition to the
above surface treatment.
[0040] Among these white particles, it is preferable to use
titanium oxide or zinc oxide in view of minimization of coloration
at high temperature and reflectance of elements due to refractive
index.
[0041] Listed as an aqueous polymer which is substantially
insoluble in electrolyte solvent according to the present invention
may be water-soluble polymer and polymer which dispersed in water
based solvent.
[0042] As polymers applicable to the present invention, there can
be listed, for example, protein such as gelatin, or gelatin
derivatives; cellulose derivatives; natural compounds including
polysaccharides such as starch, gum arabic, dextran, pullulan,
carrageenan; and synthetic polymers such as polyvinyl alcohol,
polyethylene glycol, polyvinyl pyrrolidone, acrylamide polymers, or
derivatives thereof. The gelatin derivatives include acetyl gelatin
and phthalic gelatin. The polyvinyl alcohol derivatives include
terminal alkyl group-modified polyvinyl alcohol and terminal
mercapto group-modified polyvinyl alcohol. The cellulose
derivatives include hydroxyethyl cellulose, hydroxypropyl
cellulose, and carboxymethyl cellulose.
[0043] In addition, there are also usable those described in
Research Disclosure and on pages 71-75 of Unexamined Japanese
Patent Application Publication (hereinafter referred to as JP-A)
No. 64-13546; highly water-absorbing polymers, described in U.S.
Pat. No. 4,960,681 and JP-A No. 62-245260, that is, homopolymers of
vinyl monomers containing --COOM or --SO.sub.3 M (wherein M is a
hydrogen atom or an alkali metal), or copolymers of these monomers
or copolymers of the same with other monomers (for example, sodium
methacrylate, ammonium methacrylate, or potassium acrylate). These
binders may be used in combinations of at least 2 types.
[0044] In the present invention, preferably employed may be gelatin
and derivatives thereof, or polyvinyl alcohol and derivatives
thereof.
[0045] Listed as polymers dispersed in water based solvents may be
latexes such as natural rubber latex, styrene butadiene rubber,
butadiene rubber, nitrile rubber, chloroprene rubber, heat curable
resins which are prepared by dispersing, in water based solvents,
polyisocyanate based, epoxy based, acryl based, silicone based,
polyurethane based, urea based, phenol based, formaldehyde based,
epoxy-polyamide based, melamine based, or alkyd based resins, or
vinyl based resins. Of these polymers, it is preferable to employ
water based polyurethane resins described in JP-A No. 10-76621.
[0046] "Being substantially insoluble in electrolyte solvents", as
described in the present invention, is defined as a state in which
the dissolved amount per kg of the electrolyte solvents is 0-10 g
in the temperature range of -20 to 120.degree. C. It is possible to
determine the above dissolved amount employing the methods known in
the art, such as a weight measuring method, or a component
quantitative method utilizing liquid chromatogram and gas
chromatogram.
[0047] In the present invention, a preferred embodiment of the
aqueous mixture of water based compounds and white pigments is
dispersed in water with the dispersion methods known in the art.
The mixing ratio of water based compounds/titanium oxide is
preferably in the range of 1-0.01 in terms of volume ratio, but is
more preferably in the range of 0.3-0.05.
[0048] In the present invention, a media on which the aqueous
mixture of the water based compounds and white pigments is coated
may be located anywhere as long as they are located on the
structural components between the counter electrodes of the display
element. However, it is preferable that they are provided on at
least one of the above counter electrodes. Examples of media
providing methods include a coating system, a liquid spraying
system, a spraying method via a gas phase, such as a system which
jets liquid droplets employing vibration of a piezoelectric element
such as a piezoelectric system ink-jet head, a BUBBLE JET
(registered trade name) ink-jet head which ejects liquid droplets
employing a thermal head utilizing bumping, and a spray system in
which liquid is sprayed via air or liquid pressure.
[0049] An appropriate coating system may be selected from any of
the coating systems known in the art, and examples thereof include
an air doctor coater, a blade coater, a rod coater, a knife coater,
a squeeze coater, an impregnation coater, a reverse roller coater,
a transfer roller coater, a curtain coater, a double roller coater,
a slide hopper coater, a gravure coater, a kiss roller coater, a
bead coater, a cast coater, a spray coater, a calender coater, and
an extrusion coater.
[0050] Methods to dry the aqueous mixture of water based compounds
and white pigments provided on the medium are not particularly
limited as long as they facilitate water evaporation. Examples
thereof include heating employing a heating source, a heating
method employing infrared radiation, and a heating method utilizing
electromagnetic induction. Further, water evaporation may be
performed under reduced pressure.
[0051] The term "porous" referred to in the present invention is of
a penetrating state capable of inducing silver dissolution and
deposition reaction and enabling ion species to move between
electrodes, wherein a porous white scattering substance is formed
by coating and drying the dispersion on an electrode, and an
electrolyte liquid incorporating silver or a compound containing
silver in its chemical structure is applied on the scattering
substance, followed by being sandwiched with opposed electrodes to
produce a potential difference between the opposed electrodes.
[0052] In the display element of the present invention, during
coating and drying of the aforesaid water based dispersion or after
drying thereof, the above water based dispersion is preferably
hardened using a hardener.
[0053] As examples of hardeners used in the present invention,
there are listed, for example, hardeners described in column 41 of
U.S. Pat. No. 4,678,739, ibid. No. 4,791,042, and JP-A Nos.
59-116655, 62-245261, 61-18942, 61-249054, 61-245153, and 4-218044.
More specifically, there are exemplified aldehyde based hardeners
(e.g. formaldehyde), aziridine based hardeners, epoxy based
hardeners, vinyl sulfone based hardeners (e.g.,
N,N'-ethylene-bis(vinylsulfonylacetamido)ethane), N-methylol based
hardeners (e.g., dimethylol urea), boric acid, metaboric acid, or
polymer hardeners (compounds described, for example, in JP-A No.
62-234157). When gelatin is used as a polymer, of these hardeners,
a vinyl sulfone based hardener and a chlorotriazine based hardener
are preferably used individually or in combination. Further, when a
polyvinyl alcohol is used, a boron-containing compound such as
boric acid or metaboric acid is preferably used.
[0054] There are used 0.001-1 g of, preferably 0.005-0.5 g of these
hardeners per 1 g of the water based compound. Further, to enhance
film strength, it is optionally possible to carry out heat
treatment or moisture controlling during hardening reaction.
[Compounds Represented by Formula (1) and Formula (2)]
[0055] The display element of the present invention is
characterized in containing in the electrolyte a compound
represented by Formula (A) and further at least one compound
represented by the aforesaid Formula (1) or Formula (2).
[0056] In Formula (1), R.sub.7 and R.sub.8 each represent a
substituted or unsubstituted hydrocarbon group which includes a
straight chain or a branched chain. The hydrocarbon group may
contain one or more nitrogen atoms, oxygen atoms, phosphor atoms,
sulfur atoms, or halogen atoms. When the hydrocarbon group forms a
ring which contains a sulfur atom as a ring member, the ring is not
an aromatic ring. Further, the atoms adjacent to the sulfur atom
are preferably carbon atoms.
[0057] Examples of groups which may be substituted in the
hydrocarbon groups are as follows: an amino group, a guanidino
group, a quaternary ammonium group, a hydroxyl group, a halogenated
compound, a carboxylic acid group, a carboxylate group, an amide
group, a sulfinic acid group, a sulfonic acid group, the sulfate
group, a phosphonic acid group, a phosphate group, a nitro group
and a cyano group.
[0058] In order to produce dissolution and deposition of silver,
generally, it is required to solubilize silver in an electrolyte.
The common method is, for example, to incorporate a compound which
has a chemical species that interacts with silver to form a
coordination bond or a weak covalent bond with silver, and
resulting in changing silver or the compound containing silver in
the molecule into a soluble compound. Known chemical species
described above are: a halogen atom, a mercapto group, a carboxyl
group and an imino group. In the present invention, a thioether
group effectively works as a silver dissolving agent with showing
only a small effect to the other coexisting compounds and having a
specific feature of high solubility in the solvent.
[0059] Specific examples of the compound represented by Formula (1)
will now be listed, but the present invention is not limited to the
exemplified compounds. [0060] 1-1: CH.sub.3SCH.sub.2CH.sub.2OH
[0061] 1-2: HOCH.sub.2CH.sub.2SCH.sub.2CH.sub.2OH [0062] 1-3:
HOCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2OH [0063] 1-4:
HOCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2OH
[0064] 1-5:
HOCH.sub.2CH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2SCH.-
sub.2CH.sub.2OH [0065] 1-6:
HOCH.sub.2CH.sub.2OCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2OCH.-
sub.2CH.sub.2OH [0066] 1-7: H.sub.3CSCH.sub.2CH.sub.2COOH [0067]
1-8: HOOCCH.sub.2SCH.sub.2COOH [0068] 1-9:
HOOCCH.sub.2CH.sub.2SCH.sub.2CH.sub.2COOH [0069] 1-10:
HOOCCH.sub.2SCH.sub.2CH.sub.2SCH.sub.2COOH [0070] 1-11:
HOOCCH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2C-
OOH [0071] 1-12:
HOOCCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH(OH)CH.sub.2SCH.sub.2CH.s-
ub.2SCH.sub.2CH.sub.2COOH [0072] 1-13:
HOOCCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH(OH)CH(OH)CH.sub.2SCH.sub-
.2CH.sub.2SCH.sub.2CH.sub.2COOH [0073] 1-14:
H.sub.3CSCH.sub.2CH.sub.2CH.sub.2NH.sub.2 [0074] 1-15:
H.sub.2NCH.sub.2CH.sub.2SCH.sub.2CH.sub.2NH.sub.2 [0075] 1-16:
H.sub.2NCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2NH.sub.2
[0076] 1-17: H.sub.3CSCH.sub.2CH.sub.2CH(NH.sub.2)COOH [0077] 1-18:
H.sub.2NCH.sub.2CH.sub.2OCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub-
.2OCH.sub.2CH.sub.2NH.sub.2 [0078] 1-19:
H.sub.2NCH.sub.2CH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub-
.2SCH.sub.2CH.sub.2NH.sub.2 [0079] 1-20:
H.sub.2NCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub-
.2SCH.sub.2CH.sub.2NH.sub.2 [0080] 1-21:
HOOC(NH.sub.2)CHCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2CH(NH.s-
ub.2)COOH [0081] 1-22:
HOOC(NH.sub.2)CHCH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub-
.2SCH.sub.2CH(NH.sub.2)COOH [0082] 1-23:
HOOC(NH.sub.2)CHCH.sub.2OCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub-
.2OCH.sub.2CH(NH.sub.2)COOH [0083] 1-24:
H.sub.2N(.dbd.O)CCH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.su-
b.2SCH.sub.2C(.dbd.O)NH.sub.2 [0084] 1-25:
H.sub.2N(O.dbd.)CCH.sub.2SCH.sub.2CH.sub.2SCH.sub.2C(O.dbd.)NH.sub.2
[0085] 1-26:
H.sub.2NHN(O.dbd.)CCH.sub.2SCH.sub.2CH.sub.2SCH.sub.2C(O.dbd.)NHNH.sub.2
[0086] 1-27:
H.sub.3C(O.dbd.)NHCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2NHC(O-
.dbd.)CH.sub.3 [0087] 1-28:
H.sub.2NO.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SO.sub.-
2NH.sub.2 [0088] 1-29:
NaO.sub.3SCH.sub.2CH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2CH.su-
b.2SO.sub.3Na [0089] 1-30:
H.sub.3CSO.sub.2NHCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2NHO.s-
ub.2SCH.sub.3 [0090] 1-31:
H.sub.2N(NH)CSCH.sub.2CH.sub.2SC(NH)NH.sub.2.2HBr [0091] 1-32:
H.sub.2N(NH)CSCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2SC(NH)NH.-
sub.2.2HCl [0092] 1-33:
H.sub.2N(NH)CNHCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2NHC(NH)N-
H.sub.2.2HBr [0093] 1-34:
[(CH.sub.3).sub.3NCH.sub.2CH.sub.2SCH.sub.2CH.sub.2SCH.sub.2CH.sub.2N(CH.-
sub.3).sub.3].sup.2+.2Cl.sup.-
##STR00003## ##STR00004##
[0094] Of these exemplified compounds, the exemplified compound 1-2
is specifically preferable from the viewpoint of sufficiently
producing the targeted effects of the present invention.
[0095] Then, the compound represented by Formula (2) will now be
described.
[0096] In above Formula (2), M represents a hydrogen atom, a
metallic atom, or a quaternary ammonium. Z represents a
nitrogen-containing heterocycle, and n represents an integer of
0-5. R.sub.9 represents a hydrogen atom, a halogen atom, an alkyl
group, an aryl group, an alkylcarbonamide group, an arylcarbonamide
group, an alkylsulfonamide group, an arylsulfonamide group, an
alkoxy group, an aryloxy group, an alkylthio group, an arylthio
group, an alkylcarbamoyl group, an arylcarbamoyl group, a carbamoyl
group, an alkylsulfamoyl group, an arylsulfamoyl group, a sulfamoyl
group, a cyano group, an alkylsulfonyl group, an arylsulfonyl
group, an alkoxycarbonyl group, an aryloxycarbonyl group, an
alkylcarbonyl group, an arylcarbonyl group, an acyloxy group, a
carboxyl group, a carbonyl group, a sulfonyl group, an amino group,
a hydroxy group, or a heterocyclic group. When n represents at
least 2, R.sub.9 each may be the same or different and each may be
joined to form a condensed ring.
[0097] The metallic atom represented by M in Formula (2) includes,
for example, Li, Na, K, Mg, Ca, Zn, and Ag. The quaternary ammonium
includes, for example, NH.sub.4, N(CH.sub.3).sub.4,
N(C.sub.4H.sub.9).sub.4, N(CH.sub.3).sub.3C.sub.12H.sub.25,
N(CH.sub.3).sub.3C.sub.16H.sub.33, and
N(CH.sub.3).sub.3CH.sub.2C.sub.6H.sub.5.
[0098] The nitrogen-containing heterocycle represented by Z in
Formula (2) includes, for example, a tetrazole ring, a triazole
ring, an imidazole ring, an oxadiazole ring, a thiadiazole ring, an
indole ring, an oxazole ring, a benzoxazole ring, a benzimidazole
ring, a benzothiazole ring, a benzoselenazole ring, and a
naphthoxazole ring. Among them, a triazole ring is preferable.
[0099] The halogen atom represented by R.sub.9 in Formula (2)
includes, for example, a fluorine atom, a chlorine atom, a bromine
atom, and an iodine atom. The alkyl group represented thereby
includes, for example, a methyl group, an ethyl group, a propyl
group, an i-propyl group, a butyl group, a t-butyl group, a pentyl
group, a cyclopentyl group, a hexyl group, a cyclohexyl group, an
octyl group, a dodecyl group, a hydroxyethyl group, a methoxyethyl
group, a trifluoromethyl group, and a benzyl group. The aryl group
includes, for example, a phenyl group and a naphthyl group. The
alkylcarbonamide group includes, for example, an acetylamino group,
a propionylamino group, and a butyroylamino group. The
arylcarbonamide group includes, for example, a benzoylamino group.
The alkylsulfonamide group includes, for example, a
methanesulfonylamino group and an ethanesulfonylamino group. The
arylsulfonamide group includes, for example, a benzenesulfonylamino
group and a toluenesulfonylamino group. The aryloxy group includes,
for example, a phenoxy group. The alkylthio group includes, for
example, a methylthio group, an ethylthio group, and a butylthio
group. The arylthio group includes, for example, a phenylthio group
and a tolylthio group. The alkylcarbamoyl group includes, for
example, a methylcarbamoyl group, a dimethylcarbamoyl group, an
ethylcarbamoyl group, a diethylcarbamoyl group, a dibutylcarbamoyl
group, a piperidylcarbamoyl group, and a morpholylcarbamoyl group.
The arylcarbamoyl group includes, for example, a phenylcarbamoyl
group, a methylphenylcarbamoyl group, an ethylphenylcarbamoyl
group, and a benzylphenylcarbamoyl group. The alkylsulfamoyl group
includes, for example, a methylsulfamoyl group, a dimethylsulfamoyl
group, an ethylsulfamoyl group, a diethylsulfamoyl group, a
dibutylsulfamoyl group, a piperidylsulfamoyl group, and a
morpholylsulfamoyl group. The arylsulfamoyl group includes, for
example, a phenylsulfamoyl group, a methylphenylsulfamoyl group, an
ethylphenylsulfamoyl group, and a benzylphenylsulfamoyl group. The
alkylsulfonyl group includes, for example, a methanesulfonyl group
and an ethanesulfonyl group. The arylsulfonyl group includes, for
example, a phenylsulfonyl group, a 4-chlorophenylsulfonyl group,
and a p-toluenesulfonyl group. The alkoxycarbonyl group includes,
for example, a methoxycarbonyl group, an ethoxycarbonyl group, and
a butoxycarbonyl group. The aryloxycarbonyl group includes, for
example, a phenoxycarbonyl group. The alkylcarbonyl group includes,
for example, an acetyl group, a propionyl group, and a butyroyl
group. The arylcarbonyl group includes, for example, a benzoyl
group and an alkylbenzoyl group. The acyloxy group includes, for
example, an acetyloxy group, a propionyloxy group, and a
butyroyloxy group. The heterocyclic group includes, for example, an
oxazole ring, a thiazole ring, a triazole ring, a selenazole ring,
a tetrasol ring, an oxadiazole ring, a thiadiazole ring, a thiazin
ring, triazine ring, a benzoxazole ring, a benzothiazole ring, an
indolenine ring, a benzoselenazole ring, a naphthothiazole ring, a
triazaindolizine ring, a diazaindolizine ring, and a
tetraazaindolizine ring. These substituents may further have a
substituent.
[0100] Specific examples, which are preferable, of the compound
represented by Formula (2) will now be listed that by no means
limit the scope of the present invention.
##STR00005## ##STR00006## ##STR00007## ##STR00008## ##STR00009##
##STR00010## ##STR00011## ##STR00012## ##STR00013##
[0101] Of these exemplified compounds, the exemplified compounds
2-12 and 2-18 are specifically preferable from the viewpoint of
sufficiently producing the targeted effects.
[0102] In the display element of the present invention, the
condition specified by the following expression (1) is satisfied,
provided that [X] is the molar concentration of a halogen ion and
halogen atom contained in an electrolyte and is expressed in
mol/kg; and [Ag] is the total molar concentration of silver and a
compound containing the silver in its chemical structure, contained
in the electrode and is expressed in mol/kg.
0.ltoreq.[X]/[Ag].ltoreq.0.01. Expression (1)
[0103] The halogen atom referred to in the present invention refers
to an iodine atom, a chlorine atom, a bromine atom, or a fluorine
atom. When [X]/[Ag] is more than 0.01, X.sup.-.fwdarw.X.sub.2 is
induced during oxidation-reduction reaction of silver, and then
X.sub.2 dissolves blackened silver by readily undergoing
cross-oxidation with the blackened silver, which becomes one of the
factors decreasing memory capability. Therefore, the molar
concentration of a halogen atom is preferably as low as possible
with respect to that of silver. In the present invention, the
relationship of 0.ltoreq.[X]/[Ag].ltoreq.0.001 is more preferable.
When halogen ions are added, with regard to the halogen species,
the sum of the molar concentration of each of the halogen species
is preferably [I]<[Br]<[Cl]<[F] from the viewpoint of
enhancing memory capability.
(Solvent in Electrolyte)
[0104] To the electrolyte of the present invention, any solvents
may be used together with the electrolyte to the extent that the
targeted effects of the present invention are not adversely
affected. Specifically, there can be listed tetramethylurea,
sulfolane, dimethylsulfoxide, 1,3-dimethyl-2-imidazolidinone,
2-(N-methyl)-2-pyrrolidinone, hexamethylphospholtriamide,
N-methylpropioneamide, N,N-dimethylacetamide, N-methylacetamide,
N,N-dimetylformamide, N-metylformamide, butylonitrile,
propionitrile, acetonitrile, acetylacetone, 4-methyl-2-pentanone,
2-butanol, 1-butanol, 2-propanol, 1-propanol, ethanol, methanol,
acetic anhydride, ethyl acetate, ethyl propionate, dimethoxyethane,
diethoxyfuran, tetrahydrofuran, ethylene glycol, diethylene glycol,
triethylene glycol monobutyl ether, and water. Of these solvents,
at least one type of solvent, featuring a freezing point of at most
-20.degree. C. and a boiling point of at least 120.degree. C., is
preferably contained.
[0105] Solvents employable in the present invention include
compounds described in J. A. Riddick, W. B. Bunger, T. K. Sakano,
"Organic Solvents", 4th ed., John Wiley & Sons (1986); Y.
Marcus, "Ion Solvation", John Wiley & Sons (1985); C.
Reichardt, "Solvents and Solvent Effects in Chemistry", 2nd ed.,
VCH (1988); and G. J. Janz, R. P. T. Tomkins, "Nonaquaeous
Electrolytes Handbook", Vol. 1., Academic Press (1972).
[0106] In the present invention, the electrolyte solvent may be a
single kind of solvent or a solvent mixture. However, a mixed
solvent containing ethylene carbonate is preferable. The amount of
ethylene carbonate added is preferably from 10% by weight--90% by
weight based on the total electrolyte solvent weight. A
specifically preferable electrolyte solvent is a mixed solvent of
propylene carbonate/ethylene carbonate at a weight ratio of
7/3-3/7. When the propylene carbonate ratio is more than 7/3, poor
ion conductivity is exhibited, resulting in decreased response
speed. When the ratio is less than 3/7, an electrolyte tends to be
deposited at low temperatures.
(Electrolyte-Silver Salt)
[0107] In the display element of the present invention, there can
be used silver salt compounds known in the art such as silver
iodide, silver chloride, silver bromide, silver oxide, silver
sulfide, silver citrate, silver acetate, silver behenate, silver
p-toluenesulfonate, silver salts of mercapto compounds, and silver
complexes of iminodiacetic acids. Of these, it is preferable to
use, as silver salts, compounds without a nitrogen atom exhibiting
coordination capability with a halogen, carboxylic acid, or silver,
and for example, silver p-toluenesulfonate is preferable.
[0108] The concentration of silver ions contained in the
electrolyte of the present invention is preferably in the range of
0.2 mol/kg.ltoreq.[Ag].ltoreq.2.0 mol/kg. When the silver ion
concentration is less than 0.2 mol/kg, a diluted silver solution is
formed to lower the driving rate, while when it exceeds 2 mol/kg,
solubility is degraded, which tends to result in inconvenience of
deposition during low temperature storage.
[0109] In the display element of the present invention, in addition
to the components described above, various constituent layers may
be provided, if appropriate.
(Porous Electrode Incorporating Metal Oxide)
[0110] Further, in the display element of the present invention, a
porous electrode incorporating a metal oxide can also be used.
[0111] In the display element of the present invention, it was
found that when, of the opposed electrodes, the electrode on the
side of no image observation was protected with a porous electrode
incorporating a metal oxide, oxidation-reduction reaction of silver
or a compound containing silver in its chemical structure on the
side of no image observation occurred on or within the porous
electrode incorporating the metal oxide. Accordingly, the option of
selecting the type of the electrode on the side of no image
observation can be broadened and the durability thereof can be
enhanced.
[0112] A metal oxide constituting the porous electrode of the
present invention includes, for example, titanium oxide, silicon
oxide, zinc oxide, tin oxide, Sn-doped indium oxide (ITO),
antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), and
aluminum-doped zinc oxide, or a mixture thereof.
[0113] The porous electrode is formed via bonding or contacting of
plural particles of any of the above metal oxide. The average
particle diameter of the metal oxide fine particles is preferably 5
nm-10 .mu.m, more preferably 20 nm-1 .mu.m. Further, the specific
surface area of the metal oxide particles is preferably
1.times.10.sup.-3-1.times.10.sup.2 m.sup.2/g, more preferably
1.times.10.sup.-2-10 m.sup.2/g. Still further, any appropriate
shape such as the amorphous, acicular, or spherical one is
employable as the shape of the metal oxide particles.
[0114] As the forming or bonding method of metal oxide particles, a
sol-gel method and a firing method known in the art are employable,
including, methods described, for example, in 1) Journal of the
Ceramic Society of Japan, 102, 2, P 200 (1994), 2) Yogyo Kyokai
Shi, 90, 4, p 157, and 3) J. of Non-Cryst. Solids, 82, 400 (1986).
Further, there can be used a method in which titanium oxide
dendrimer particles prepared using a gas phase method are coated on
a substrate via dispersion on a solution and then a solvent is
removed by drying at a temperature of about 120--about 150.degree.
C. to obtain a porous electrode. The metal oxide particles are
preferably in the state of being bonded, and further in the state
where a resistance of at least 0.1 g, preferably at least 1 g, is
exhibited, based on measurement using a continuous weight surface
measurement system (e.g., a scratch tester).
[0115] The term "porous" referred to in the present invention is of
a penetrating state where a porous electrode is arranged and then a
potential difference is produced between opposed electrodes, which
enables induction of silver dissolution and deposition reaction and
enables ion species to move in the porous electrode.
(Electron Insulating Layer)
[0116] In the display element of the present invention, an electron
insulating layer can be provided.
[0117] It is only necessary for an electron insulating layer
applicable to the present invention to be a layer exhibiting ion
conductivity as well as electron insulating properties. There are
listed, for example, a solid electrolyte film in the form of film
of a polymer with a polar group or a salt; a pseudo-solid
electrolyte film composed of a porous film, exhibiting high
electron insulating properties, in the voids of which an
electrolyte is held; a polymer porous film having voids; and a
porous body of an inorganic material such as a silicon-containing
compound featuring a low specific dielectric constant.
[0118] As a forming method of a porous film, there can be used any
appropriate method known in the art such as a firing method (fusing
method) (utilizing pores created among particles prepared by
partially fusing polymer fine particles or inorganic particles via
addition of a binder); an extraction method (in which a constituent
layer is formed using an organic or inorganic substance soluble in
a solvent and a binder insoluble in the solvent, followed by
dissolving the organic or inorganic substance with the solvent to
obtain fine pores); a foaming method of allowing a high molecular
weight polymer to foam by heating or degassing; a phase conversion
method of allowing a mixture of polymers to be phase-separated by
use of a good solvent and a poor solvent; and a radiation exposure
method of forming pores via exposure of various kinds of
radiations.
[0119] Specifically, there can be listed the electron insulating
layers described in JP-A Nos. 10-30181, 2003-107626; Examined
Japanese Patent Application Publication No. 7-95403; and Japanese
Patent Publication Nos. 2635715, 2849523, 2987474, 3066426,
3464513, 3483644, 3535942, and 3062203.
(Electrolyte Materials)
[0120] In the display element of the present invention, the
electrolyte can appropriately incorporate any of the following
compounds when the electrolyte is liquid. Examples of the compounds
include a potassium compound such as KCl, KI, or KBr; a lithium
compound such as LiBF.sub.4, LiClO.sub.4, LiPF.sub.6, or
LiCF.sub.3SO.sub.3; and a tetraalkylammonium compound such as
tetraethylammonium perchlorate, tetrabutylammonium perchlorate,
tetraethylammonium borofluoride, tetrabutylammonium borofluoride,
or tetrabutylammonium halide. Further, there can preferably be used
the fused salt electrolyte compositions described in Paragraph Nos.
[0062]-[0081] of JP-A No. 2003-187881. Still further, there can
also be used a compound which forms an oxidation-reduction pair
such as I.sup.-/I.sub.3.sup.-, Br.sup.-/Br.sub.3.sup.-, or
quinone/hydroquinone.
[0121] Further, when being solid, a solid electrolyte can
incorporate any of the following compounds exhibiting electron or
ion conductivity.
[0122] Examples of the compounds include a fluorinated vinyl based
polymer containing perfluorosulfonic acid; polythiophene;
polyaniline; polypyrrole; a triphenylamine; a polyvinylcarbazole; a
polymethylphenylsilane; a calcogenide such as Cu.sub.2S, Ag.sub.2S,
Cu.sub.2Se, or AgCrSe.sub.2; a fluorine-containing compound such as
CaF.sub.2, PbF.sub.2, SrF.sub.2, LaF.sub.3, TlSn.sub.2F.sub.5, or
CeF.sub.3; a lithium salt such as Li.sub.2SO.sub.4,
Li.sub.4SiO.sub.4, Li.sub.3PO.sub.4; and a compound such as
ZrO.sub.2, CaO, Cd.sub.2O.sub.3, HfO.sub.2, Y.sub.2O.sub.3,
Nb.sub.2O.sub.5, WO.sub.3, Bi.sub.2O.sub.3, AgBr, AgI, CuCl, CuBr,
CuBr, CuI, LiI, LiBr, LiCl, LiAlCl.sub.4, LiAlF.sub.4, AgSBr,
C.sub.5H.sub.5NHAg.sub.5I.sub.6, Rb.sub.4
Cu.sub.16I.sub.7Cl.sub.13, Rb.sub.3Cu.sub.7Cl.sub.10, LiN,
Li.sub.5NI.sub.12, or Li.sub.6NBr.sub.3.
[0123] Still further, a gel-like electrolyte can also be used as a
supporting electrolyte. When an electrolyte is nonaqueous, there
can be used the oil gelling agents described in Paragraph Nos.
[0057]-[0059] of JP-A No. 11-185836.
(Thickeners to be Added to the Electrolyte)
[0124] In the display element of the present invention, there can
be used a thickener for the electrolyte, including gelatin, gum
arabic, poly(vinyl alcohol), hydroxyethyl cellulose, hydroxypropyl
cellulose, cellulose acetate, cellulose acetate butyrate,
poly(vinylpyrrolidone), poly(alkylene glycol), casein, starch,
poly(acrylic acid), poly(methylmethacrylic acid), poly(vinyl
chloride), poly(methacrylic acid), copoly(styrene-maleic
anhydride), copoly(styrene-acrylonitrile),
copoly(styrene-butadiene), a poly(vinyl acetal) (e.g., poly(vinyl
formal) and poly(vinyl butyral)), a poly(ester), a poly(urethane),
a phenoxy resin, poly(vinylidene chloride), a poly(epoxide), a
poly(carbonate), poly(vinyl acetate), a cellulose ester, and a
poly(amide); and including, as a transparent hydrophobic binder,
polyvinylbutyral, cellulose acetate, cellulose acetate butyrate,
polyester, polycarbonate, poly(acrylic acid), and polyurethane.
[0125] These thickeners may be used in combinations of at least 2
types. There are further listed the compounds described on pages
71-75 of JP-A No. 64-13546. Of these, a compound preferably used
includes a polyvinyl alcohol, a polyvinylpyrrolidone, a
hydroxypropyl cellulose, and a polyalkylene glycol, from the
viewpoint of enhancement of compatibility with various types of
additives and of dispersion stability of white particles.
(Other Additives)
[0126] The constituent layers of the display element of the present
invention include auxiliary layers such as a protective layer, a
filter layer, an antihalation layer, a crossover light cutting
layer, and a backing layer. These auxiliary layers may incorporate,
as appropriate, chemical sensitizers, noble metal sensitizers,
photosensitive dyes, supersensitizers, couplers, high boiling point
solvents, antifoggants, stabilizers, development inhibitors, bleach
accelerators, fixing accelerators, color mixing inhibitors,
formalin scavengers, toning agents, hardeners, surfactants,
thickeners, plasticizers, lubricants, UV absorbents,
anti-irradiation dyes, filter light absorbing dyes, fungicides,
polymer latexes, heavy metals, antistatic agents, and matting
agents.
[0127] The additives described above are detailed in Research
Disclosure (hereinafter referred to simply as RD), Vol. 176,
Item/17643 (December 1978), RD, Vol. 184, Item/18431 (August 1979),
RD, Vol. 187, Item/18716 (November 1979), and RD, Vol. 308,
Item/308119 (December 1989).
[0128] Types of compounds shown in three of these RD articles are
listed below with the described portions thereof.
TABLE-US-00001 RD 17643 RD 18716 RD 308119 Additive Page &
Class Page & Class Page & Class Chemical 23 III 648 upper
96 III Sensitizer right Sensitizing 23 IV 648-649 996-8 IV Dye
Desensitizing 23 IV 998 IV Dye Dye 25-26 VIII 649-650 1003 VIII
Development 29 XXI 648 upper Accelerator right Antifoggant, 24 IV
649 upper 1006-7 VI Stabilizer right Whitening 24 V 998 V Agent
Hardener 26 X 651 left 1004-5 X Surface 26-7 XI 650 right 1005-6 XI
Active Agent Antistatic 27 XII 650 right 1006-7 XIII Agent
Plasticizer 27 XII 650 right 1006 XII Lubricant 27 XII Matting
Agent 28 XVI 650 right 1008-9 XVI Binder 26 XXII 1003-4 IX Support
28 XVII 1009 XVII
[0129] A metallocene derivative can be used in a constitution layer
of the display element of the present invention. A ferrocene
derivative is preferably used as an example of a metallocene
derivative. Specific examples of a ferrocene derivative are:
ferrocene, methylferrocene, dimethylferrocene, ethylferrocene,
propylferrocene, n-butylferrocene, t-butylferrocene, and
1,1-dicarboxylferrocene. A metallocene derivative can be used
singly or used as a mixture of two or more metallocene
derivatives.
(Layer Structure)
[0130] The constituent layers between the opposed electrodes in the
display element of the present invention will now further be
described.
[0131] As a constituent layer according to the display element of
the present invention, a constituent layer incorporating a positive
hole transport material can be provided. The positive hole
transport material includes, for example, an aromatic amine, a
triphenylene derivative, an oligothiophene compound, a polypyrrole,
a polyacetylene derivative, a polyphenylene vinylene derivative, a
polythienylene vinylene derivative, a polythiophene derivative, a
polyaniline derivative, a polytoluidine derivative, CuI, CuSCN,
CuInSe.sub.2, Cu(In,Ga)Se, CuGaSe.sub.2, Cu.sub.2O, CuS,
CuGaS.sub.2, CuInS.sub.2, CuAlSe.sub.2, GaP, NiO, CoO, FeO,
Bi.sub.2O.sub.3, MoO.sub.2, and Cr.sub.2O.sub.3.
(Substrate)
[0132] As a substrate usable in the present invention, there are
also preferably used a synthetic plastic film including a
polyolefin such as polyethylene or polypropylene, a polycarbonate,
cellulose acetate, polyethylene terephthalate, polyethylene
dinaphthalene dicarboxylate, a polystyrene naphthalate, polyvinyl
chloride, polyimide, a polyvinyl acetal, and polystyrene. A
syndiotactic structure polystyrene is also preferable. These can be
prepared via the methods described, for example, in each of JP-A
Nos. 62-117708, 1-46912, and 1-178505. Further, there are
exemplified metal substrates such as stainless steel; paper
supports such as baryta paper or resin coated paper; supports
prepared by arranging a reflection layer on any of the above
plastic films; and those which are described in JP-A No. 62-253195
(pages 29-31) as supports. There can also preferably be used those
described on page 28 of RD No. 17643; from the right column of page
647 to the left column of page 648 of RD No. 18716; and on page 879
of RD No. 307105. As these substrates, there can be used those
heat-treated at a temperature of at most Tg so that core-set curl
is decreased, as described in U.S. Pat. No. 4,141,735. Further, any
of these supports may be surface-treated to enhance adhesion of the
support to other constituent layers.
[0133] In the present invention, there may be employed, as surface
treatment, glow discharge treatment, ultraviolet irradiation
treatment, corona discharge treatment, and flame treatment.
Further, the supports described on pages 44-149 of Kochi Gijutsu
(Known Techniques), No. 5 (issued on Mar. 22, 1991, published by
Aztech Corp.) may be used. Still further, there are listed those
described on page 1009 of RD, No. 308119, and in "Supports" of
Product Licensing Index, Vol. 92, Page 108. In addition, glass
substrates, and epoxy resins kneaded with glass powder are
employable.
(Electrodes)
[0134] In the display element of the present invention, at least
one of the opposed electrodes is preferably a metal electrode. For
the metal electrode, there can be used a metal known in the art
such as platinum, gold, silver, copper, aluminum, zinc, nickel,
titanium, or bismuth, and alloys thereof. For the metal electrode,
preferable are metals exhibiting a work function close to the
oxidation-reduction potential of silver in an electrolyte. Of
these, a silver electrode or an electrode having a silver content
of at least 80% is advantageous to maintain a reduced state of
silver, which is also superior in anti-staining of the electrode.
As preparation methods of the electrode, there can be used
conventional ones such as a vapor deposition method, a printing
method, an ink-jet method, a spin coating method, and a CVD
method.
[0135] Further, in the display element of the present invention, at
least one of the opposed electrodes is preferably a transparent
electrode. The transparent electrode is not specifically limited if
being transparent and electrically conductive. Examples thereof
include Indium Tin Oxide (ITO: indium tin oxide), Indium Zinc Oxide
(IZO: indium zinc oxide), fluorine-doped tin oxide (FTO), indium
oxide, zinc oxide, platinum, gold, silver, rhodium, copper,
chromium, carbon, aluminum, silicon, amorphous silicon, and BSO
(Bismuth Silicon Oxide). To form an electrode in such a manner, for
example, mask deposition via a method of sputtering an ITO film on
a substrate, or patterning via a photolithographic method after
formation of the entire ITO film may be carried out. The surface
resistance value is preferably at most 100 .OMEGA./.quadrature.,
more preferably at most 10 .OMEGA./.quadrature.. The thickness of
the transparent electrode is not specifically limited, but is
commonly 0.1-20 .mu.m.
(Other Components of Display Element)
[0136] For the display element of the present invention, any
appropriate sealing agent, columnar structure substance, and spacer
particle are employable, if appropriate.
[0137] The sealing agent, functioning to enclose the content in
order not to leak out, is also referred to as an enclosing agent.
As the sealing agent, there are employable curable type resins
including thermally curable, light curable, moisture curable, or
anaerobically curable resins such as epoxy resins, urethane resins,
acrylic resins, vinyl acetate reins, ene-thiol resins, silicone
resins, or modified polymer resins.
[0138] The columnar structure substance provides strong
self-holding force (strength) between the substrates, including,
for example, columnar structure substances such as cylindrical,
square pole, elliptically cylindrical, and trapezoidally
cylindrical substances, wherein these substances are arranged so as
to form a predetermined pattern such as a grid at regular
intervals. A stripe arrangement at predetermined intervals may be
also employed. The columnar structure substance is not arranged at
random, but preferably arranged in such a manner as to
appropriately hold the distance between the substrates, and not to
inhibit displaying images, wherein the columnar structure substance
is arranged at regular intervals, in a pattern in which the
intervals are gradually varied, or in a predetermined pattern
repeated at regular intervals. When the ratio of the display area
of the display element occupied by the columnar structure substance
is in the range of 1% -40%, the display element exhibits
practically adequate strength.
[0139] A spacer may be placed between a pair of the substrates to
uniformly hold the gap thereof. As the spacer, spherical objects of
resins or inorganic oxides are exemplified. Further, an adhesive
spacer, the surface of which is coated with a thermoplastic resin,
may suitably be used. To uniformly hold the gap between the
substrates, the columnar structure substance may be provided by
itself, and both of the spacer and the columnar structure substance
may be also provided. Further, instead of the columnar structure
substance, the spacer may be used by itself as a space-holding
member. When a columnar structure is formed, the diameter of the
spacer is equivalent to at most the height of the columnar
structure substance, but is preferably equal to the height thereof.
When no columnar structure substance is formed, the diameter of the
spacer is equivalent to the cell gap thickness.
(Screen Printing)
[0140] In the present invention, a sealing agent, a columnar
structure substance, and an electrode pattern may be formed via a
screen printing method. In the screen printing method, the
electrode surface of a substrate is covered with a screen having a
predetermined pattern, followed by placing a printing material
(being a composition, to form the columnar structure substance,
such as radiation curable resins) on the screen. Subsequently, a
squeegee is moved at a predetermined pressure, angle, and rate,
whereby the printing material is transferred onto the substrate via
the screen pattern. Then, the transferred material is thermally
cured and dried.
[0141] When the columnar structure substance is formed via the
screen printing method, resin materials to be used are not limited
to the radiation curable resins. For example, thermally curable
resins or thermoplastic resins such as epoxy resins or acrylic
resins may be also used. Examples of the thermoplastic resins
include polyvinyl chloride resins, polyvinylidene chloride resins,
polyvinyl acetate resins, polymethacrylate resins, polyacrylate
resins, polystyrene resins, polyamide resins, polyethylene resins,
polypropylene resins, fluorine resins, polyurethane resins,
polyacrylonitrile resins, polyvinyl ether resins, polyvinyl ketone
resins, polyether resins, polyvinyl pyrrolidone resins, saturated
polyester resins, polycarbonate resins, and chlorinated polyether
resins. These resin materials are preferably used in a paste form
prepared by dissolving corresponding resins in appropriate
solvents.
[0142] After the columnar structure substance has been formed on
the substrate as described above, a spacer is provided on at least
one of the substrates, as appropriate, and then a pair of the
substrates are stacked to form an empty cell, wherein the
electrode-forming surfaces are faced each other. A display cell is
obtained by bonding a pair of the stacked substrates via heat
application under pressure applied from both sides thereof. To
prepare a display element, an electrolyte composition is injected
between the substrates, for example, via a vacuum injection method.
Alternatively, in the bonding process of the substrates, a liquid
crystal component may be enclosed just before bonding of the
substrates, after the electrolyte component has been dripped on one
of the substrates.
(Driving Method of Display Element)
[0143] In the display element of the present invention, it is
preferable to perform a driving operation such that blackened
silver is deposited by applying a voltage of at least the
deposition overpotential and the deposition of blackened silver is
continued by applying a voltage of at most the deposition
overpotential. Performance of such a driving operation results in
reduced writing energy, reduced load of the drive circuit, and
enhanced writing speed as an image screen. Existence of
overpotential in electrode reaction is generally known in the
electrochemistry field. The overpotential is detailed, for example,
on page 121 of "Denshi-ido no Kagaku/Denkikagaku Nyumon (Chemistry
of Electron Transfer/Introduction to Electrochemistry)" (1996,
published by Asakura Shoten). The display element of the present
invention is also regarded as electrode reaction of an electrode
with silver in an electrolyte so that existence of an overpotential
in silver dissolution and deposition is readily understood. Since
the magnitude of an overpotential is controlled by an exchange
current density, from the fact that after formation of blackened
silver, deposition of blackened silver can be continued via
application of a voltage of at most a deposition overpotential, it
is presumed that the surface of blackened silver has less excess
energy, resulting in easy electron injection.
[0144] The driving operation for the display element of the present
invention is either a simple matrix drive or an active matrix
drive. In the present invention, the simple matrix drive refers to
a driving method, in which current is successively applied to a
circuit formed by vertically crossing of an anode line containing
plural anodes to a facing cathode line containing plural cathodes.
The use of the simple matrix drive has the advantage that the
circuit structure and the driving IC can be simplified to reduce
the production cost. The active matrix drive refers to a driving
method, in which scanning lines, data lines, and current supplying
lines are formed on a grid, and driving is carried out via TFT
circuits positioned in each of the grids. The active matrix drive
is advantageous in gradation and memory functions since a switching
function is allocated to each pixel. The circuit described, for
example, in FIG. 5 of JP-A 2004-29327 is employable.
(Commercial Applications)
[0145] The display element of the present invention is applied to
fields including electronically published books, ID cards, public
use, transportation, broadcasting, financial clearance, and
distribution and logistics. Specific examples include door keys,
student ID cards, employee ID cards, membership cards, convenience
store cards, department store cards, vending machine cards, gas
station cards, subway and railroad cards, bus cards, cashing cards,
credit cards, highway cards, driver's license cards, hospital
consultation cards, electronic medical charts, health insurance
cards, basic resident registers, passports, and electronic
books.
EXAMPLES
[0146] The present invention will now specifically be described
with reference to examples, but the scope of the present invention
is not limited to them. Incidentally, "part" or "%" to be shown in
the examples represents "part by weight" or "% by weight" unless
otherwise specified.
Example 1
<<Preparation of Display Element>>
(Preparation of Display Element 1)
(Preparation of Electrolyte Liquid 1)
[0147] To 2.5 g of dimethyl sulfoxide was added 90 mg of sodium
iodide, 50 mg of example compound (2-19), 75 mg of silver iodide,
and 0.1 g of ethylmethylimidazolium-bistrifluoromethanesulfonimide.
After the mixture was completely dissolved, 150 mg of
polyvinylpyrrolidone (average molecular weight of 15,000) was added
and the mixture was stirred for 1 hour with heating at 120.degree.
C. to obtain electrolyte liquid 1.
(Preparation of Electrode 1)
[0148] An ITO (Indium Tin Oxide) film having a pitch of 145 .mu.m
and a width of 130 .mu.m was formed on a glass substrate of a size
of 2 cm.times.4 cm with a thickness of 1.5 mm using a commonly
known method to obtain a transparent electrode (electrode 1).
(Preparation of Electrode 2)
[0149] A silver-palladium electrode (electrode 2) having an
electrode thickness of 0.8 .mu.m, a pitch of 145 .mu.m and a
distance between the electrodes of 130 .mu.m was formed on a glass
substrate of a size of 2 cm.times.4 cm with a thickness of 1.5 mm
using a commonly known method to obtain electrode 2.
(Preparation of Electrode 3)
[0150] An isopropanol mixture liquid was prepared by ultrasonic
dispersion of 20 weight % of titanium oxide with isopropanol
containing 2 weight % of polyvinyl alcohol (having an average
polymerization degree of 3500 and a saponification degree of 87%).
Thus prepared isopropanol mixture liquid was applied with a
thickness of 100 .mu.m on electrode 2 on the edge of which was
coated with an olefinic sealing agent containing 10 volume % of
glass beads having an average particle size of 40 .mu.m. Then the
coated isopropanol mixture liquid was dried at 15.degree. C. for 30
minutes so as to evaporate the solvent, and was further dried at
15.degree. C. for 30 minutes to obtain electrode 3.
(Preparation of Display Element)
[0151] Electrode 3 and electrode 1 were bonded together in such a
manner that the striped form electrodes crossed at a right angle,
then followed by heat pressing to prepare an empty cell.
Electrolyte liquid 1 was vacuum injected into the empty cell, and
the injection inlet was sealed with an epoxy-based ultraviolet
curable resin to prepare Display Element 1.
(Preparation of Display Element 2)
[0152] Display Elements 2 was prepared in the same manner as in
preparation of Display Element 1 except that example compound
(2-19) in electrolyte liquid 1 was exchanged with example compound
(1-2).
(Preparation of Display Element 3)
[0153] Display Elements 3 was prepared in the same manner as in
preparation of Display Element 1 except that
ethylmethylimidazolium-bistrifluoromethanesulfonimide in
electrolyte liquid 1 was exchanged with the same amount of
azacyclopentane-1-spiro-1'-azacyclobutyl-p-toluenesulfonic
acid.
(Preparation of Display Element 4)
[0154] Display Elements 4 was prepared in the same manner as in
preparation of Display Element 1 except that
ethylmethylimidazolium-bistrifluoromethanesulfonimide in
electrolyte liquid 1 was exchanged with the same amount of
azacyclohexane-1-spiro-1'-azacyclobutyl-p-toluenesulfonic acid.
(Preparation of Display Element 5)
[0155] Display Elements 5 was prepared in the same manner as in
preparation of Display Element 4 except that example compound
(2-19) in the electrolyte liquid was exchanged with example
compound (1-2).
(Preparation of Display Element 6)
[0156] Display Elements 6 was prepared in the same manner as in
preparation of Display Element 1 except that
ethylmethylimidazolium-bistrifluoromethanesulfonimide in
electrolyte liquid 1 was exchanged with the same amount of
spiro-(1,1')-biazacyclobutyl-p-toluenesulfonic acid.
(Preparation of Display Element 7)
[0157] Display Elements 7 was prepared in the same manner as in
preparation of Display Element 3 except that dimethyl sulfoxide,
silver iodide and example compound (2-19) in electrolyte liquid 1
were each respectively exchanged with the same amount of propylene
carbonate, silver p-toluenesulfonate and example compound
(2-12).
(Preparation of Display Element 8)
[0158] Display Elements 8 was prepared in the same manner as in
preparation of Display Element 7 except that
azacyclohexane-1-spiro-1'-azacyclobutyl-p-toluenesulfonic acid in
the electrolyte liquid was exchanged with the same amount of
spiro-(1,1')-biazacyclobutyl-p-toluenesulfonic acid.
(Preparation of Display Elements 9-16)
[0159] Display Elements 9-16 were prepared in the same manner as in
preparation of Display Element 8 except that the amount of sodium
iodide in the electrolyte liquid were each respectively changed to
0 mg, 5.28 mg, 7.2 mg, 46 mg, 0.53 mg, 0.72 mg, 0.47 mg, and 0.23
mg.
<Evaluation of Display Elements>
(Resistance of Color Change)
[0160] The driving condition for each of display elements thus
prepared were determined so as to exhibit L* value of 65 using
spectrophotometer CM-3700d (produced by Konica Minolta Sensing,
Inc.). Then the obtained driving condition was applied to display
elements to produce white color state. L* value, a* value and b*
value of the produced white color state were measured. They were
denoted as L.sub.1, a.sub.1 and b.sub.1 respectively. Display
elements were subjected to 1000 times of repeated change of
whitening-blackening using the same driving condition. Then L*
value, a* value and b* value of the produced white color state were
measured to give L.sub.2, a.sub.2 and b.sub.2.
[0161] From each of the measured values, the evaluation value for
color change were calculated by the equation:
.DELTA.E=[(L.sub.2-L.sub.1).sup.2+(a.sub.2-a.sub.1).sup.2+(b.sub.2-b.sub-
.1).sup.2].sup.1/2.
The relative value of .DELTA.E for each display element was
determined by setting .DELTA.E for Display Element 1 to be 1. The
obtained results were shown in Table 1. The smaller the .DELTA.E,
the color change under repeated driving condition is small and the
property of display element is indicated to be good.
TABLE-US-00002 TABLE 1 Display Resistance of Element Color Change
[X]/[Ag] No. .DELTA.E value value Remarks 1 1.00 3.68 Comp. 2 1.08
3.68 Comp. 3 0.75 2.87 Inv. 4 0.77 2.87 Inv. 5 0.74 2.87 Inv. 6
0.57 2.87 Inv. 7 0.56 1.85 Inv. 8 0.40 1.85 Inv. 9 0.28 0 Inv. 10
0.39 0.11 Inv. 11 0.40 0.15 Inv. 12 0.42 1.00 Inv. 13 0.41 0.011
Inv. 14 0.39 0.015 Inv. 15 0.29 0.010 Inv. 16 0.28 0.005 Inv.
[0162] From the results shown in Table 1, the display elements
having the constitution of the present invention have a reduced
color change an superior to others after repeated driving.
Example 2
[0163] The similar superior effects were obtained from the display
elements prepared by changing example compound (1-2) used in
Example 1 to example compounds (1-3) or (1-4), and also example
compound (2-19) was changed to example compounds (2-18) or
(2-17).
* * * * *